A basic task of traffic control systems in cities is online determination of the traffic flows in the road network in order to obtain information about the traffic situation and optimally control the connected subsystems. This involves systems for determining the traffic situation on a wide-area basis, but also for precisely determining traffic conditions in subnetworks and optimizing associated traffic signal installations. An essential task of these methods is to determine the traffic flows in the road network, calculation of the turning flows at intersections being a central algorithmic problem.
A method of the abovementioned type is known from the dissertation “Ein Verfahren zur gekoppelten Schätzung von Kantenbelastungen, Abbiegequoten and Störungen in Stadtstraβennetzen” (A method for combined estimation of edge loadings, turning rates and traffic incidents in urban road networks), published in the series of publications of the automation systems working group of the Technische Universitat Hamburg-Harburg, Issue 20, May 2001. The estimator is supplied at two-second intervals with all the measured traffic volumes flowing into and out of an intersection. For turning rate estimation a purely dynamic method is used which is also classifiable among the recursive methods. A highly time-resolved mode of calculation automatically results in subdivision into phase group oriented subsystems. For calculating the turning rates, the variations in the entry and exit flows are taken into account in a time interval k compared to the preceding time interval k−1. This known method is characterized by exacting requirements in terms of data provision—e.g. aggregation of measurement data in intervals of two to three seconds—and complex network modeling. In some cases quite specific positions for the measurement cross-sections are also required. For the model equation used as the basis for the estimation method, as a time reference either the same measuring interval is used for the left- and right-hand side or the exit traffic volume at measuring interval k is calculated from the entry traffic volumes of the preceding time interval k−1. This method suffers from the disadvantage that the estimation result is strongly dependent on the travel times between the measurement cross-sections of the subnetwork in question.